HARRISBURG (AP) — Paul Addis, a former energy executive and a first-time candidate for public office, is joining the GOP field vying to challenge Pennsylvania's Democratic U.S. Sen. Bob Casey in 2018.

Addis is making a formal announcement of his candidacy Wednesday. The 63-year-old Addis lives in suburban Philadelphia after a career spent in energy, including as a top executive at AEP Corp. of Ohio and Louis Dreyfus Highbridge Energy of Connecticut.

Addis is something of a maverick. He wrote in Arizona Sen. John McCain for president instead of voting for Donald Trump. He takes moderate Republican positions on gun control and immigration policy, and criticizes the Republican Party as prioritizing power over ideas.

Addis joins a GOP field of roughly a half-dozen political unknowns. Two Republican congressmen are also considering running.